The field of the invention is plastic components and, more particularly, the invention relates to automotive parts made of thermoplastic materials that are stable at elevated temperatures and materials for making, methods of manufacture of the same.
A modern automobile is manufactured from a large number of parts. Each of the parts that make up an automobile typically has a number of desired properties that are distinct to a particular part. In a particular automobile part, it may be more or less desirable for the part to be lighter or heavier, more rigid or flexible, or paintable or not.
For those parts that comprise the xe2x80x9cbody in whitexe2x80x9d of an automobile, that is the parts that pass through an automobile assembly plant""s painting operation, the ability to withstand high temperatures is desirable so that important manufacturing efficiencies can be obtained. In normal vehicle assembly operations, vehicle subassemblies are subject to electro-coating at temperatures in excess of 390xc2x0 F. and, after painting, vehicle subassmblies are cycled through paint drying ovens where they are exposed to temperatures in excess of 270xc2x0 F. It is important that parts passing through these conditions do so in good condition. One problem that can arise at these temperatures is the release of xe2x80x9cmolded-inxe2x80x9d stress contained in the part that changes the shape of the part or compromises the strength of the part
This is because many components are assembled to a vehicle, including the front end of the vehicle, require precise alignment and durable mounting mechanisms. Headlights, fenders, fascia and a radiator are examples of parts that may be attached directly or indirectly to a grill opening reinforcement. Grill opening reinforcements have been found to be helpful in tying together such components with the forward section of front fenders and the frame of a vehicle as it is being assembled. Other integrated front end modules that support other parts include bumper reinforcements, radiator supports, and inner fender reinforcements. These parts are relatively large and must maintain close tolerances for critical dimensions to meet strict fit and finish standards.
Traditionally, automobile parts for the xe2x80x9cbody in whitexe2x80x9d parts have been made from metal because of the tolerance of those materials for the temperatures of the painting operations of the modern automotive industry. For example, grill opening reinforcements and other integrated front end modules have been manufactured from a plurality of sheet metal stampings that are either welded or fastened together.
Metal parts have the disadvantage of being heavy and not as easily formed as plastic parts. Metal integrated front end modules are heavy and add to the overall vehicle weight thereby decreasing the fuel efficiency of the automobile. While metal parts have the benefits of being strong and easily surviving high temperature environments, they can be also unacceptably expensive. Being formed in multiple pieces, metal integrated front end modules require labor intensive assembly operations. Quality control is required to assure proper location of the mounting mechanisms for multiple parts assembled to the integrated front end module.
Recently, sheet molding compound (SMC) has been used to manufacture grill opening reinforcements. SMC grill opening reinforcements are generally slightly less weight than metal grill opening reinforcements. However, for the manufacture of certain parts, such as grill opening reinforcements (GORs), thermoset plastic part, such as those made from sheet molding compound (SMC), cannot readily have necessary features molded into them. Rather, SMC grill opening reinforcements require a substantial investment in tooling for both molding the SMC and finishing the SMC parts after molding. It is generally necessary to machine a SMC grill opening reinforcement by drilling, purring or shaping with a router fastener holes and locating surfaces. Also, the SMC process is relatively slow requiring a large number of mold cavities to manufacture parts on a production basis. SMC is also not a recyclable material which means that at the end of the car""s life cycle or if there is any scrap in manufacturing process, it is necessary to dispose of the SMC grill opening reinforcement in landfill instead of recycling. This is because the thermoset plastic, once set, can only be recycled by rendering the part into ash that can only be resold for a minimal economic recovery.
Some exterior auto and truck parts such as fenders, quarter panels, doors, trim parts bumpers, fender extensions and other molded exterior parts of are currently made of moldable thermoplastic polymers to obtain resistance to permanent deformation on impact and corrosion resistance. Typical moldable thermoplastic polymers that are being use for these parts are polypropylene, styrenics, and various heteroatom polymers. While such polymers can be molded into auto and truck parts that are substantially lighter than currently used sheet metal parts, they have limitations. In particular, such parts ordinarily do not pass through industry-standard standard painting operations with acceptable strength and durability. Further, such molded plastic parts have molded-in stress that releases when the part is exposed to heat, such as in a painting operation, thereby altering the dimensions or shape of the part. The release of the molded-in stress leads to unacceptable fit and finish of parts to other parts, and can lead to unacceptable deviations in the alignment of connected parts.
Prior technology has been developed to utilize injection molded thermoplastic parts that are attached to automobile vehicle bodies prior to electro-coating and paint drying oven exposure but are expensive. Exposure of large weight bearing parts to high temperatures results in a loss of dimensional stability since the weight of parts attached to injection molded parts causes the injection molded parts to sag. This results in poor fit and finish and difficulties in assembling components after being exposed to high temperatures. Further, parts must not only demonstrate adequate fit and finish in the short term, but must have adequate torsional stability to prevent cracking. For example, grin opening reinforcements are subject to torque while the automobile is being driven, especially if the road has bumps or holes. A strong, but brittle, part can eventually crack or even fail, which is an unacceptable outcome.
Therefore, there is a need for dimensionally stable parts that exhibit torsional stability and can survive high temperature painting operations. It would be advantageous if such parts could be made from materials that are less expensive and more recyclable than existing parts exhibiting sufficient dimensional stability, torsional stability, and high temperature tolerance.
A number of patents relate to various aspects of motor vehicle component technology. For example, U.S. Pat. Nos. 6,293,615 and 6,287,442 to Tarahomi, disclose an injection molded thermoplastic integrated front end reinforcement made from a fiber reinforced thermoplastic polymer that includes at least 65% post-consumer recycled polyethylene terephthalate. The patents disclose that the polyethylene terephthalate is reinforced with at least 45% glass fibers and mineral filled. The ""615 and ""442 patents which are commonly owned, are incorporated by reference into this application as if fully set forth herein.
U.S. Pat. No. 6,136,249 to Takeuchi et al. discloses a process for producing a bumper made of synthetic resin that includes a core and an outer layer covering the core. The ""249 patent is incorporated by reference into this application as if fully set forth herein.
U.S. Pat. Nos. 5,814,673 and 6,180,685 to Khait disclose methods of making polymeric particulates wherein polymeric scrap material, virgin polymeric material and compounds thereof are supplied to intermeshing extruder screws which are rotated to transport the polymeric material along their length and subject the polymeric material to solid state shear pulverization and in-situ polymer compatibalization, if two or more incompatible polymers are present. The ""673 and ""685 patents are incorporated by reference into this application as if filly set forth herein.
U.S. Pat. No. 5,503,790 to Clements discloses a crack-proof and resilient article made of PET that is produced from about 40% to 90% regrind PET. The article is characterized in that it ha an intrinsic viscosity between 0.54 and 0.68. The ""790 patent is incorporated by reference into this application as if fully set forth herein.
U.S. Pat. No. 5,789,470 to Herbst et al. discloses stabilized recycled plastics comprising macrocylic compounds where the macrocycle contains at least 8 atoms. Herbst et al. also disclose a process for stabilizing recycled plastic compounds using such macrocycle compounds. The ""470 patent is incorporated by reference into this application as if fully set forth herein.
U.S. Pat. No. 5,561,186 to Nagaoka et al discloses a resin composition suitable for recycling comprising polyphenylene ether, polyamide, and alkali metal earth oxide, and with optional use of a compatibilizing agent, rubbery material, and inorganic filler. The ""186 patent is incorporated by reference into this application as if fully set forth herein.
U.S. Pat. No. 5,881,508 to Irvine et al. discloses a decking extension made from extruded plastic material. The decking extension can be made from a pure material or a combination of two materials one of which is a recycled plastic material. The ""508 patent is incorporated by reference into this application as if fully set forth herein.
U.S. Pat. No. 5,876,644 to Nichols et al. discloses a method of recycling post-consumer polyester to obtain recycled polyester of sufficiently high purity to meet food packaging requirements. The method includes cleaning contaminated pieces of post-consumer polyester to remove surface contaminants, melting the surface-cleaned post-consumer polyester, extruding the post consumer melt, blending the melt of post-consumer polyester with a melt of virgin polyester prepolymer, solidifying and pelletizing the blended melt while the virgin polyester prepolymer remains as a prepolymer and polymerizing the solid blended pellets in the solid state. The ""644 patent is incorporated by reference into this application as if fully set forth herein.
U.S. Pat. Nos. 5,312,573, 5,523,328 and U.S. Patent Application Publication US 2001/0008322 to Rosenbaum et al. disclose process and apparatus for extruding compounds of thermoplastic and thermoset materials and products made therefrom. By continuously extruding a heated compound of whole tire waste and thermoplastic binder material. The material may be extruded into a continuously cooled, open-ended casting chamber, or can be through a die into a hollow form to form a filled article. The ""573, ""328 and U.S. Patent Application Publication US 2001,0008322xe2x80x2 are incorporated by reference into this application as if fully set forth herein.
U.S. Pat. No. 5,503,788 to Lazareck et al. discloses a method for processing a compound raw automobile shredder residue and virgin and/or contaminated synthetic plastic material. Automobile shredder residue produced by a conventional automobile shredder is formed into a first stream by being ground into a first granulating zone to a reasonably small granular size using conventional equipment. A second stream comprising virgin and/or contaminated synthetic plastics material is ground in a second granulating zone. The two streams are combined to provide a processable compound. The processable compound is introduced into a high intensity mixer. The processable compounds are transformed into a semi-molten discharge stream by the kinetic energy imparted to the processable compound by the mixer and are simultaneously vented by the mixer. The semi-molten compound is then passed on to an extruder or press to form a mass of desired shape, and then cooled. The ""788 patent is incorporated by reference into this application as if fully set forth herein.
U.S. Pat. Nos. 5,302,419 and 5,360,661 to Muzzy et al. which discloses apparatus and methods related to flexible towpreg articles made of reinforcing filaments and a matrix forming material made from recycled plastics wherein the reinforcing filaments are substantially wetout by the matrix forming material such that the towpreg plies have a low void content compared to the multiply towpreg. The ""419 and ""661 patents are incorporated by reference into this application as if fully set forth herein.
U.S. Pat. Nos. 5,217,660 and 5,266,396 to Howard disclose methods of recycling expanded polystyrene foam materials. Unexpanded virgin polystyrene beads having pentane gas contained therein are thermal expanded to produce a supply of expanded beads. Then, a supply of used polystyrene foam is obtained and ground into pieces of small proportions. The used polystyrene foam pieces are then placed in contact with pentane gas. The expanded beads are thereafter combined to form a compound which preferably contains not less than 50% by weight foam pieces. The compound is then place in a mold under heat and pressure to produce a final product. The ""660 and ""396 patents are incorporated by reference into this application as if fully set forth herein.
U.S. Pat. No. 5,089,571 to Bonk et al. discloses high molecular weight thermoplastic resins with narrow molecular weight distribution and good physical properties that are prepared by regenerating thermally degraded and/or off-grade thermoplastic polyurethane resins. The regenerated high molecular weight thermoplastic resins are disclosed as not presenting any processing difficulties inherent to high molecular weight resins. The ""571 patent is incorporated by reference into this application as if fully set forth herein.
U.S. Pat. Nos. 3,976,730 and 4,063,860 to Cushing disclose a method for employing scrap thermoplastic resin in an extruder. The method is for utilizing a high percentage of thermoplastic scrap resins with additional virgin thermoplastic resin in a screw-type extruder. The ""730 and ""860 patents are incorporated by reference into this application as if fully set forth herein
U.S. Pat. No. 4,1338,374 to Currie is a process for manufacturing a shaped article of polyester material by extruding a molten blend of scrap poster and virgin polyester. The molten blend is created by feeding the scrap polyester and virgin polyester into a poymerizing stream that is maintained at elevated temperature and reduced pressure. The ""374 patent is incorporated by reference into this application as if fully set forth herein